Leads (catheters) for a wide variety of medical procedures, such as Deep Brain Stimulation (DBS) and cardiac interventions, are typically placed into the body of a subject under stereotactic guidance, fluoroscopy, or other methods. Stereotactic guidance is a static method based on high resolution images taken prior to the procedure and does not take into account displacement of the brain caused by the loss of cerebral spinal fluid (CSF), blood or simple brain tissue displacement by the surgical tool. It is therefore often necessary to perform a real time physiological localization of the target area to augment and verify the previously obtained stereotactic data by observing the patients response to stimulation through the DBS electrodes or by recording and displaying (visual or audible) the action potentials of individual neurons along the path way to the target zone using microelectrodes. These additional steps are time consuming; resulting in procedures between 6–8 hours with a failure rate still remaining between 20–30%.
Cardiac procedures are mainly performed using X-ray fluoroscopy. Because X-ray shadows are the superposition of contributions from many structures, and since the discrimination of different soft tissues is not great, it is often very difficult to determine exactly where the catheter is within the heart. In addition, the borders of the heart are generally not accurately defined, so it is generally not possible to know whether the catheter has penetrated the wall of the heart. Furthermore, lesions are invisible under x-ray fluoroscopy. Thus, it is very difficult to discern whether tissue has been adequately ablated.